The present invention relates to a two-dimensional surface light emitting element array and a method and apparatus for driving it, and more particularly to a two-dimensional surface light emitting element array capable of shortening a time required for patterned light emission of one frame and reducing power consumption on signal wirings to restrict generation of heat and a method and apparatus for driving it.
One example of previously known two-dimensional surface light emitting element arrays in a matrix wiring format is disclosed as a two-dimensional surface light emitting laser array in e.g. "PHOTONICS TECHNOLOGY LETTERS" issued 1994, Vol. 6, pages 913 to 917. FIG. 11 shows such a two-dimensional surface light emitting laser array composed of vertical resonator type surface light emitting laser elements 102 arranged in a two-dimensional array on a semi-insulating semiconductor substrate 101. Each of the surface light emitting semiconductor lasers 102 is provided with an anode electrode 103 having an opening 103a. The anode electrode 103 is connected to a row wiring 104 having a row pad 105 at its end. A cathode electrode is connected to a column wiring 107 on the semiconductor substrate 101. The column wiring 107 is connected to a column pad 108. The respective columns of the two-dimensional surface light emitting lasers 102 arranged in an array are isolated by high resistance layers 109 formed by ion-implantation.
In the configuration described above, the row wirings 104 are selected in order by a clock signal. When the voltage corresponding to an image data is applied to column wirings 107 in synchronism with this, a light emission pattern corresponding to the image signal can be obtained.
FIG. 12 shows a two-dimensional surface light emitting laser array in a matrix wiring format having n.times.m (32.times.120=3840) surface light emitting lasers 102. In this array, 3840 surface light emitting lasers 102 are arranged at the intersecting points of 32 lines of row wirings 104 and 120 lines of column wirings 107.
FIG. 13 shows a driving apparatus for making patterned light emission of the two-dimensional light emission laser array. The driving apparatus includes first 12 (twelve) shift registers 11 for receiving image data 16 serially simultaneously on the basis of the clock 10, 12 (twelve) latch circuits 12 for receiving the image data from the first shift registers 11 simultaneously in parallel on the basis of a latch signal 17, 12 (twelve) drivers 13 connected to a power supply Vss, each of them serving to supply driving signals to corresponding 10 (ten) column wirings 107 in accordance with the image data latched in the latch circuit 12, a second shift register 14 for shifting a transfer signal 18 on the basis of the clock 10, a selector 15 connected to power source Vcc for selecting a row wiring 104 on the basis of the shifting position of the transfer signal 18 in the second shift register 14, and 3840 surface light emitting lasers 102 arranged at the intersecting points of the row wirings 104 and the column wirings 107, each represented by a resistance R and a laser diode LD.
FIG. 14 shows operation timings of driving the two-dimensional surface light emitting laser array. Using clock 10, the image data of ten bits are simultaneously supplied to each of the first twelve shift registers 11. Thus, the image data 16 having a total of 120 bits are allotted to the 120 column wirings 107. By the latch signal 17, the image data are latched in the latch circuit 12. At the same timing as the latch signal 17, the transfer signal 18 is produced and supplied to the second shift register 14. When the transfer signal 18 is located at the first bit of the second shift register 14, the selector 15 selects the row wiring 104 at j=1 by producing a select signal. Then, the driver 13 supplies the column wirings 107 from i=1 to i=120 in accordance with the image data latched in the twelve latch circuits 12. As a result, on the row wiring 104 at j=1, the surface light emitting laser(s) 102 having received the driving signal "1" through the column wiring(s) 107 emit(s) light whereas the surface light emitting laser(s) 102 having received the driving signal "0" does not emit light. The duration of such an operation is 20 ns.
Next, the transfer signal 18 is shifted to the second bit position of the second shift register 14. Simultaneously, the subsequent 120 bits image data 16 are supplied to the first registers 11 and latched in the latch 12. Therefore, the selector 15 selects the row wiring 104 at j=2. The driver 13 causes the surface light emitting laser (s) on the selected row wiring 104 to emit light. In this way, the row wirings 104 are selected sequentially from j=1 to j=32 so that display of the light emission pattern of one frame is completed.
In the above operation, since the surface light emitting lasers 102 are sequentially driven in a time-divisional manner for a duration of 20 ns, the time T taken for the light emission pattern of one frame is
T=3840.times.20 ns/120 PA1 =640 ns PA1 T=3840.times.20 ns/12 PA1 =6.4 .mu.s PA1 T=3840.times.20 ns/1 PA1 =76.8 .mu.s PA1 a wiring matrix including a first wiring group of plural electrodes arranged in parallel to each other, a second wiring group of plural electrodes arranged in parallel to each other and crossing the first wiring group; and PA1 plural surface light emitting elements connected to respective electrodes of said first wiring group and said second wiring group and arranged two-dimensionally at the intersecting points of said first wiring group and said second wiring group, wherein PA1 at least one of said first wiring group and said second wiring group includes plural groups of electrodes separated electrically in a wiring direction of the electrodes; and PA1 the electrodes of one of said electrode groups are provided with an external connection section for driving said surface light emitting elements connected to the electrodes individually from the surface light emitting elements connected to the electrodes of the remaining electrode groups.
FIG. 15 shows another driving device for driving the two-dimensional surface light emitting laser array as shown in FIG. 12 to make patterned light emission. This driving device is different from the driving device shown in FIG. 13 in that it further comprises a third shift register 19 for shifting a second transfer signal 20 on the basis of the clock 10 for divisional driving of the column wirings 107 and AND circuits 21 arranged in a pattern of divisional driving and taking a logical product of the outputs from the third shift register 19 and latch circuit 12 so that it is supplied to the driver 13.
FIG. 16 shows operation timings of driving the two-dimensional surface light emitting laser array shown in FIG. 12 by the driving device shown in FIG. 15. First, the row wiring 104 at j=1 is selected for a duration of 200 ns. The column wirings 107 at i=1 to 120 are divided into ten groups of wirings each having twelve surface light emitting lasers 102, i.e., i=1, 11, . . . 111, i=2, 12, . . . 112, . . . . . . i=10, 20, . . . 120 in accordance with the shifting position of the transfer signal 20 in the third shift register 19. In the above duration of 200 ns, each group of wirings is driven for a duration of 20 ns. Next, the row wiring 104 at j=2 is selected. Likewise, the column wirings 107 are driven in a divisional manner. In this way, the row wirings to j=32 are selected sequentially. By the selection of each of the row wirings 104, the surface light emitting lasers 102 are driven divisionally on the basis of divisional driving of the column wirings 107. Thus, patterned light emission of one frame is performed.
In the above operation, since for each of the row wirings 104, ten groups each having twelve two-dimensional surface light emitting lasers 102 are driven divisionally, the time T required to obtain one frame patterned light emission is
FIG. 17 shows another driving device for driving the two-dimensional surface light emitting laser array as shown in FIG. 12 to make patterned light emission. This driving device is different from the driving device shown in FIG. 15 in that it further comprises a third shift register 19 for shifting a second transfer signal 20 on the basis of the clock 10 and AND circuits 21 arranged in a pattern of divisional driving and taking a logical product of the outputs from the third shift register 19 and latch circuit 12 so that it is supplied to the driver 13, and in that in this configuration, by the selection of each of the row wirings 104 at j=1 to 32, the column wirings 107 at i=1 to 120 are divided into 120 so that the surface light emitting lasers 102 are driven one by one.
FIG. 18 shows operation timings of driving the two-dimensional surface light emitting laser array shown in FIG. 12 by the driving device shown in FIG. 17. First, the row wiring 104 at j=1 is selected for a duration of 2400 ns. The column wirings 107 at i=1 to 120 are divided into 120 sets of wirings each having a single surface light emitting lasers 102, i.e., i=1, 1=2, . . . . . . 120 in accordance with the shifting position of the transfer signal 20 in the third shift register 19. In the above duration of 2400 ns, each wiring is driven for a duration of 20 ns. Next, the row wiring at j=2 is selected. Likewise, the column wirings 107 are driven. In this way, the row wirings 104 to j=32 are selected sequentially. By the selection of each of the row wirings 104, the surface light emitting lasers 102 are driven divisionally on the basis of divisional driving of the column wirings 107. Thus, patterned light emission of one frame is performed.
In the above operation, since for each of the row wirings 104, each of the surface light emitting lasers 102 is driven sequentially, the time T required to obtain one frame light emission is
However, when the conventional matrix shape two-dimensional surface light emitting laser array is driven by the driving apparatus of FIG. 13, for the selected row wiring, all the corresponding surface light emission lasers connected to the selected row wiring are driven simultaneously so that the heat generated from adjacent laser elements influence on each other to deteriorate the element characteristic. In order to obviate this inconvenience, the divisional driving by the driving devices of FIGS. 15 and 17 can be proposed. Such driving, however, reduce the number of the surface light emitting lasers driven in time division, thus lengthening the time required for one frame. The power consumed in the row wirings and column wirings results in the sum of the product of the number of the surface light emitting lasers driven in time division and the resistances of the column wirings and the product of the square of the number and the resistances of the row wirings. Development of the high density two-dimensional surface light emitting element array is limited by increase of power consumption and heat generation.